1. The Field of the Invention
The field of the invention specifically relates to an apparatus for electronic storage of analog signal information.
2. Prior Art
Many devices are known in the art for the electronic storage of analog information. In a typical prior art device using digital storage techniques, the underlying information is essentially analog, such as sound, which must be stored electronically in digital form. A common analog signal to be digitally recorded is the output signal of a microphone, which is routed through an input filter to an amplifier. The amplifier supplies the signal to a sample and hold circuit. The information from the sample and hold circuit is passed through an analog-to-digital (A-to-D) converter which supplies the digital output information to memory. In order to play back the recorded sound information from the memory, the contents of the memory must first pass through a D-to-A converter to be reconverted to analog. The D-to-A converter sends its output signal through a filter to an amplifier and then to a speaker. In its essence, that is how prior art digital electronic storage of sound information is done.
Digital storage provides very good sound quality. The reproduced sound is equivalent to the input sound. The disadvantages of the prior art system are its high complexity, resulting from A-to-D and D-to-A conversions, and the large amounts of memory required for digital storage of sound information. For telephone, for example 64K bits are needed to store each second of conversation.
What is needed is a device that can electronically store analog information at reasonable precision but with substantially reduced complexity and memory requirements from what is required by digital techniques. Such a system should be designed so that small errors in recording the signal information are not damaging to the reproduction quality upon playback. The system of the present invention provides an electronic signal recording and playback apparatus which is tolerant of small errors in recording and stores signal information in considerably less memory space than that required for digital storage.